Coal distributor for stoker retorts



March 7, 1939. F, R, NELSON 7 2,150,035

COAL DIS TRIBUTOR FOR STOKER RETOBTS Filed Jan. 2, 1936 Patented Mar. 7, 1939 UNETED STATES PATENT QFFICE Transmission Corporation,

corporation of Illinois Rockford, 111., a

Application January 2, 1936, Serial No. 57,153

5 Claims.

This invention relates to underfeed stokers, and has particular reference to means for evenly distributing the feeding of coal upwardly in the retort.

The principal object of my invention is to provide, in connection with the end of the: feed screw projecting into the retort, a combination bearing and baffle arch in the retort extending over the projecting portion of the screw, the same having an elongated opening therein over the screw and lengthwise with respect thereto, specially formed with relation to the screw and retort to cause even distribution of coal and at the same time the desired breadth of bearing surface, particularly at the rearward end of the arch.

The invention is illustrated in the accompanying drawing, wherein- Figure 1 is a plan View of a stoker retort showing the coal distributor arch;

Fig. 2 is a longitudinal section on the broken line 22 of Figure 1;

Fig. 3 is a sectional detail on the line 33 of Fig. 2, looking at the end of the arch, and

Fig. 4 is a similar view showing a modified or alternative construction.

Similar reference numerals are applied to corresponding parts throughout the views.

Referring to Figs. 1 to 3, 5 is the conduit extending forwardly from a coal hopper to the retort 6 disposed under the firebox of the furnace, hot water heater, or boiler. The-latter has tuyeres 1' arranged in a rectangle over the retort, throughwhichairto support combustion is discharged in a well known manner, the air being delivered through an air duct (not shown) extending rearwardly from a blower in parallelism to the conduit 5. Dead plates 8 are disposed around the upper ends of the tuyeres to complete the bottom of the firebox. Coal is fed into the retort 6 through the conduit 5 by a screw 9. It is a problem to provide uniform distribution of this coal throughout the rectangular cross-sectional area of the retort so that the coal will not pile up at one point continually. Considerable experimenting with different constructions disclosed a tendency for one construction to cause piling up at the far end of the retort and with another at the near end, and with still another at some intermediate point. This piling up I found was due to a combination of conditions; the extent towhich the feed screw projects into the retort was found to be an important factor in determining just where the greatest height would occur in relation to the ends of the retort. The combination which I will now describe avoids the difiiculty of the coal piling up at one point and maintains an even top on the bed of coal at all feeds.

In accordance with my invention, an arch it is provided in the retort 6 extending over the projecting end portion ll of the screw 9 to serve both as a coal baliie and as a bearing for the screw, the inside surface l2 having the periphery of the thread of the screw arranged to slidably engage the same. An elongated opening 13 is provided in the arch I extending lengthwise with respect tothe screw. This opening is. to allow coal to flow upwardly through the arch directly from the screw, and it is proportioned properly with relation to the dimensions of the retort and diameter of the screw to make for uniform distribution of coal feed. The rear end of the opening is narrowed into a bottle neck, as indicated at M, for two reasons, namely, togive increased bearing surface at the end of the screw and also reduce the flow of coal through this portion of the arch to avoid piling up over the end of the screw adjacent the middle of the retort. The arch may be a separate plate having lugs l and I6 welded thereto or formed integral therewith for fastening the same to the side walls of the retort as by bolts H, or it may take the form; of the arch shown at In in Fig. 4 integral with the side walls of the retort ii, the arch being in that case either welded in place or cast integral with the retort. The bottom of the retort is formed, as best appears in Figs. 2 and 3, to pro vide a complemental bearing surface l8 for the end portion ll of the feed screw under the arch I0, and to provide an upwardly inclined surface l9 rearwardly from the end of the screw. This inclined portion of the bottom of the retort plays an important part in the operation of the stoker, as will now be described.

In operation, it will be assumed that the retort is empty at the outset. will first discharge coal at the end thereof onto the upwardly sloping bottom Hi. This continues until enough coal has been deposited beyond the screw to build up a certain resistance to further discharge of coal from the end of the screw, whereupon there commences to be a discharge of coal upwardly through the opening l3 until the resistance to flow upwardly more than balances the resistance to flow from the end of the screw. Then the discharge from the end of the screw is resumed until a greater resistance to flow at that point is developed by reason of the buildup in the depth of coal beyond the screw, whereupon coal is again discharged through the open- As the screw 9 turns, it

ing [3, and so on. The retort fills up to an even depth, that is with the top thereof level with the tuyer-es throughout the length of the retort. If it were not for the arch I0 providing support for the projecting end portion ll of the screw in the retort, this end portion might tend to flex opening l3 over the extremity of the screw, in

dicated at M, results in even distribution, but can say that actual experimenting with different shaped openings showed conclusively. that it eliminates or-minimizes the tendency for the coal to pileup adjacent the center of the retort. In this connection, I would also statethat the size of the opening l3l4 is also determined by experimenting, anclits dimensions will differ'for different sized retorts. In conclusion, it will'be V noticed that the end of the feed screw projects slightly beyond the end of the arch lull. This, too, is a condition which I have found affects the operation of the stoker. I have found that the best performance is obtained if the end of the screw is at least flush with the end of the arch or if it does not project more than, say three quarters of an inch from the end of the arch. I

It is believed the foregoing description conveys a good understanding of the objects and advantages of my invention. The appended claims have been drawn with a view to covering all legitimate modifications and adaptations.

' 1. As an article of manufacture, a stoker'feed screw retort bafile comprising an elongated arcuate plate adapted to be placed concave side down over a feed screw in the inlet end of a stoker retort, saidplate having a'longitudinally extending opening provided therein reaching from one end thereof to a point near 'the'other end,

the opening being of uniform width for a por-' tion of its length, the width representing a large fraction of the width of the plate, and said opening being narrowed abruptly to approximately half the first width and being of uniform narrow width the rest of its length. V

2. As an article of manufacture, a stoker feed ,3. In a screw type underfeed stoker, the combination of a retort having an inlet opening at 7 one end thereof, a rotary screw for feeding coal 1 through said opening into the retort,said screw projecting through said opening a certain distance into the retort representing a small fraction of the length of said retort, the 'bottom'fof the retort adjacent the inlet opening being conformed to provide bearing support for thelower half of the screw, and a substantially horizontally disposed combination screw bearing and coal discharge regulating baflie wall extending in an are over the upper half only of anappreciable length of the projecting end of said screwin said retort, said wall having bearing en'- gagement onthe inside thereof with the periphery of the thread of the screw throughout a corresponding length of the screw, said wall having an opening provided therein over said screw for restricted discharge of coal upwardly therethrough radially from the screw in addition to the unrestricted discharge of coal from the end of the screw. 1

4. A stoker as set forth in claim 3 wherein the opening provided in the baffle wall extends longitudinally thereof reaching from one end to a point near the other end, the opening being of uniform Width for a portion of its length, the

width representing a large fraction of the width of the wall, and said opening being narrowed abruptly to approximately half the first width and being of uniform length. 7

5. A stoker as set forth in claim 3 wherein the opening in the baffle wall extends longitudifnally thereof reaching from one end to a point 7 near the other end, the opening being symmetrical with respect to a longitudinal center line through said wall and being of a uniform width for about half said width for the rest of its length.

FLOYD R. NELSON.

narrow width the rest of its 

